CwazyWabbit Posted August 31, 2020 Share Posted August 31, 2020 Mickey, pretty sure the uk is -0% +10%, so the speedo could read 33mph when doing 30mph but not read any less than 30 when doing 30. Sounds the same as where Flechner is. Flechner, if you get the checksum wrong all that will happen is the needle won't move, so you can have as many goes as you like. I'm sure one of the guys who worked out the algorithm will be along to help soon. Quote Link to comment Share on other sites More sharing options...
flechner Posted September 1, 2020 Share Posted September 1, 2020 (edited) I think I got the algorithm and it is as an Excel formula: =DEC2HEX(BITAND(255;1024+BITLSHIFT(BITAND(2*(BITAND(BITRSHIFT(A1;4);32771)+BITRSHIFT(A1;12));7)+5;4)-BITXOR(BITRSHIFT(A1;8);BITAND(A1;255)));2) whereby the rate (in dec) is in the excel field "A1" (see also attached Excel file) So the checksum for a rate of 2472 (=2548 - 3%) should be 0xEF ... maybe someone knowledgable could confirm this? TD5SpeedometerAdjustmentChecksumCalc.xlsx Edited September 1, 2020 by flechner 1 Quote Link to comment Share on other sites More sharing options...
TSD Posted September 3, 2020 Share Posted September 3, 2020 I haven't looked at your spreadsheet, but I agree that 0xEF looks to be the right checksum value, it's what I get returned from my original code. 1 Quote Link to comment Share on other sites More sharing options...
andy.cowman Posted April 5 Share Posted April 5 Hello! I have read through everything and now I need to put some learning into practise! Its been a few years since this thread has been updated so not sure if this will garner any responses.... I am looking to put together bits to do it These were mentioned and used - was it successful though? https://www.aliexpress.com/item/1005005690400280.html or on amazon.... a bit more money but here tomorrow https://www.amazon.co.uk/gp/product/B08N49Y7S1/ref=ox_sc_act_title_2?smid=AI12MG02JKGW2&psc=1 I think this might allow solderless connection - seems worth a punt for £5 https://www.amazon.co.uk/gp/product/B093K5L2QY/ref=ox_sc_act_title_1?smid=A3A5E9UVDOIP4V&psc=1 I think from reading this that I don't need to power up the unit to read and write to the chip - so no need to power up the unit on the bench? The next challenge is making sure I get the right hex to update the mileage! How wrong can it go?! Quote Link to comment Share on other sites More sharing options...
TSD Posted April 5 Share Posted April 5 The clip works fine, it's what I use. But if you can solder fine wires, and only have one speedo to adjust, it's probably not worth a fiver. I didn't use the eeprom programmer, so I can't comment on that. It's a slight oddball device, so it's possible some programmers wont support it. I used a raspberry pi instead, because it was in the drawer. Not as cheap if you don't have one to hand, but at least it's still useful for something else later. ten quid for a pi zero, plus you need an sd card and maybe a serial cable, so maybe twenty quid all up? 1 Quote Link to comment Share on other sites More sharing options...
andy.cowman Posted April 5 Share Posted April 5 43 minutes ago, TSD said: The clip works fine, it's what I use. But if you can solder fine wires, and only have one speedo to adjust, it's probably not worth a fiver. I didn't use the eeprom programmer, so I can't comment on that. It's a slight oddball device, so it's possible some programmers wont support it. I used a raspberry pi instead, because it was in the drawer. Not as cheap if you don't have one to hand, but at least it's still useful for something else later. ten quid for a pi zero, plus you need an sd card and maybe a serial cable, so maybe twenty quid all up? Thanks! Had a quick check and I have an older pi and a pi400! Not tried connecting that up to anything really yet. Any advice is gratefully received! Quote Link to comment Share on other sites More sharing options...
TSD Posted April 5 Share Posted April 5 Either will do. I'd use the older pi, simply because it matters less if it all goes horribly wrong Get it set up with a keyboard and monitor, and Raspbian / RaspberryPi OS. The exact version doesn't much matter, either with a gui or without. Meanwhile I will find a big shovel and dig out the programming code... Quote Link to comment Share on other sites More sharing options...
andy.cowman Posted April 5 Share Posted April 5 you sir are a superstar! Once my little boy is asleep and his toys are away I will get mine out! Quote Link to comment Share on other sites More sharing options...
andy.cowman Posted April 5 Share Posted April 5 Got a Pi B+ V1 on the desk Quote Link to comment Share on other sites More sharing options...
TSD Posted April 5 Share Posted April 5 Sounds perfect - and probably what mine runs on too, though I'm not certain - it's a repurposed old programmer I built for a customer, and I glued the box shut so I didn't get tempted to rob the SD card for something else I just looked at the code and realised it needed a freshen up for a modern RPi, so then I had to find a speedo to check it still works... but it all looks to be working now. Sent you a PM, check your inbox. 2 Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted April 5 Share Posted April 5 Good to see this thread still getting use, can't believe it's 13 years since this got done. Quote Link to comment Share on other sites More sharing options...
Retroanaconda Posted April 5 Share Posted April 5 55 minutes ago, CwazyWabbit said: Good to see this thread still getting use, can't believe it's 13 years since this got done. And that speedo you did the original work on is still going strong 246,000 miles later - I think we can safely say the process did not cause any issues 1 Quote Link to comment Share on other sites More sharing options...
andy.cowman Posted April 5 Share Posted April 5 19 minutes ago, Retroanaconda said: And that speedo you did the original work on is still going strong 246,000 miles later - I think we can safely say the process did not cause any issues Well that's good to hear!! I am just waiting for the last bits to arrive and then another old 200tdi 90 will be following your guide! Quote Link to comment Share on other sites More sharing options...
andy.cowman Posted April 5 Share Posted April 5 1 hour ago, CwazyWabbit said: Good to see this thread still getting use, can't believe it's 13 years since this got done. I was quite surprised how quickly you all replied! Thank you very much 1 Quote Link to comment Share on other sites More sharing options...
andy.cowman Posted April 5 Share Posted April 5 2 hours ago, TSD said: Sounds perfect - and probably what mine runs on too, though I'm not certain - it's a repurposed old programmer I built for a customer, and I glued the box shut so I didn't get tempted to rob the SD card for something else I just looked at the code and realised it needed a freshen up for a modern RPi, so then I had to find a speedo to check it still works... but it all looks to be working now. Sent you a PM, check your inbox. Thank you very much!! I will get that all sorted out Quote Link to comment Share on other sites More sharing options...
pete3000 Posted April 6 Share Posted April 6 (edited) When i ran my td5 speedo up i used an old school advance j3b sig gen, analogue speed control 🙂 I found the freq point where it would drop out after the speedo was round the needle around 130+ mph (plus a bit). As i got near the mileage i wanted i throttled the frequency back to 50mph then later 20mph. Pete Edited April 6 by pete3000 Quote Link to comment Share on other sites More sharing options...
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